/Engine/Source/Runtime/Experimental/Chaos/Public/GeometryCollection/GeometryCollection.h
Note: UVs have been reworked, and unfortunately there is not a safe path to provide the original UVs managed array as a deprecated accessor. They are now stored in dynamically allocated attributes per UV channel (/ layer) See Facades/CollectionUVFacade.h for a more complete interface to access UV layers, but accesses of the form Collection.UVs[Vertex][Layer] can be replaced with Collection.GetUV(Vertex, Layer) (or ModifyUV)
FVector2f & ModifyUV ( int32 VertexIndex, int32 UVLayer )